1. Field of the Invention
The present general inventive concept relates to a display apparatus, and more particularly, to a display apparatus displaying a moving picture and a still picture using different gradation levels.
2. Description of the Related Art
Among display apparatuses displaying a group of gradations using a time-sharing method, a PDP (Plasma Display Panel) and a DMD (Digital Mirror Device) generate a false contour in a moving picture. Here, the false contour indicates a kind of an afterimage due to a gradation level difference between a moving picture area and its adjacent area, wherein the gradation level difference is visually persisted and looks like a contour.
FIG. 1 is a schematic control block diagram of a conventional PDP to attenuate a false contour of a moving picture.
As shown in FIG. 1, the PDP includes a motion detector 101, a gradation level selector (or gradation selector) 102, a gradation level converter (or gradation converter) 103 and a panel actuator 104.
The motion detector 101 detects a motion area and a still area in a picture from a picture signal to be displayed. As a detection method, there is used a motion estimation method of sampling motion vectors per regular-sized block of two consecutive frames (a former frame and a current frame), or a motion detection method of detecting a picture data change of a pixel.
The gradation level selector 102 includes a group of gradation levels for a moving picture and a group of gradation levels for a still picture and selects one of the groups according to the result of the motion detector 101.
The gradation level converter 103 converts the picture signal into one of the groups of gradation levels selected by the gradation level selector 102, and provides the converted picture signal to the panel actuator 104.
The picture corresponding to the picture signal is divided into the motion area and the still area by the motion detector 101. The picture signal in each area is provided to the panel actuator 104 after converted into a corresponding group of gradation levels by the gradation level convertor 103. Since there are few gradation levels suitable for a moving picture, the picture in motion is not visually precised thereby reducing the false contour. On the other hand, the still picture can be precisely displayed using the gradation levels suitable for the still picture.
However, if the result of the motion detector 101 for every area of the picture changes frequently, the gradation level converter 103 constantly converts the picture signal into different gradation levels. Accordingly, the same picture signals are alternatively converted into different gradation levels, and thus it becomes hard to maintain a constant gradation level with respect to the same picture signals. In other words, the conventional display apparatus selects a group of gradation levels depending on a type of the picture signal of the current frame, thereby frequently causing a flicker.